Vibratory roller compacting apparatus and method

ABSTRACT

A SELF-PROPELLED VIBRATORY MACHINE INCLUDING A FRAME RESILIENTLY MOUNTING A COMPACTING ROLLER FOR ROTATION, AND ECCENTRIC MEANS, ROTATABLE ABOUT THE ROLLER AXIS, FOR VIBRATING THE ROLLER. A VARIABLE SPEED HYDROSTATIC TRANSMISSION INCLUDING A REVERSIBLE, VARIABLE DISPLACEMENT PUMP IN CLOSED-LOOP FLUID COMMUNICATION WITH A FIXED DISPLACEMENT MOTOR IS IN CONTINUOUS DRIVING RELATIONSHIP WITH THE ECCENTRIC MEANS AND IS OPERABLE TO CONTROL THE SPEED AND DIRECTION OF ROTATION THEREOF. A CONTROL LINKAGE AUTOMATICALLY CORRELATES THE DIRECTION OF ROTATION OF ECCENTRIC MEANS WITH THE TRANSLATING DIRECTION OF TRAVEL OF THE MACHINE. POSITIVE BRAKING OF THE ECCENTRIC MEANS, IN APPROXIMATELY THREE REVOLUTIONS THEREOF, MINIMIZES THE PERIOD OF RESONANCE BETWEEN THE FRAME AND THE VIBRATING ROLLER.

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sept. zo, 1971 VIBRATORY ROLLER COMPACTING APPARATUS AND METHOD FiledApril 1. 1969 5 Sheets-Sheet 2 J. E. KEPPLER sept. zo, 1f97=1 VIBRATORYROLLER COMPACTING APPARATUS AND METHOD Filed April 1. 1969 5Sheets-Sheet 3 Ssheets-sheet 4 Sept. 20, 1971 J. E. KEPPLER VIBRATORYROLLER COMPACTING APPARATUS AND METHOD med April 1'. 1969 f8. ma um. BK.QN. \8

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Sept. 20, 1-97 J. E. KEPPLER VIBRATORY ROLLER COMPACTING APPARATUS ANDMETHOD med April 1. 1969 5 Sheets-Sheet 5 FIGTA United States Patent3,605,583 VIBRATORY ROLLER COMPACTING APPARATUS AND METHOD John E.Keppler, San Antonio, Tex., assignor to Tampo Manufacturing Company,Inc., San Antonio, Tex. Filed Apr. 1, 1969, Ser. No. 812,144 Int. Cl.E01c 19/28 U.S. Cl. 94-50V 16 Claims ABSTRACT OF 'I'HE DISCLOSURE Aself-propelled vibratory machine including a frame resiliently mountinga compacting roller for rotation, and eccentric means, rotatable aboutthe roller axis, for vibrating the roller. A variable speed hydrostatictransmission including a reversible, variable displacement pump inclosed-loop uid communication with a iixed displacement motor is incontinuous driving relationship with the eccentric means and is operableto control the speed and direction of rotation thereof. A controllinkage :automatically correlates the `direction of rotation ofeccentric means with the translating direction of travel of the machine.Positive braking of the eccentric means, in approximately threerevolutions thereof, minimizes the period of re'sonance between theframe and the vibrating roller.

BACKGROUND OF THE INVENTION This invention relates to a vibratoryroller. More particularly, this invention relates to improvements in thedr'e of a rotatable eccentric means for vibrating the ro er.

In machines for compacting ground surfaces, it is known to employ freelyrotatable rollers vibrated by eccentric means rotating independently ofthe roller. Such rollers are often resiliently suspended by a frame.

It has been common practice to rotate the eccentric means, during acompacting operation, at a speed significantly greater than the range inwhich the vibrating roller and the supporting frame are in resonance.Before reversing the direction of travel of the machine, the rotation ofthe eccentric means is usually stopped in order to avoid grooving of thecompacted surface by the vibrating roller. During the eccentric slowingprocess, either prior to a travel direction change or for any otherpurpose, the eccentric speed passes through the range in which thevibrating roller and the supporting frame are in resonance.

Within this range, portions of the impulses produced by the eccentricare stored within the system by the resilient frame suspension. Thus,heavy shocks due to increased amplitude of compacting vibration aretransmitted through the suspension to the roller and to the surface tobe compacted.

If the deceleration of the rotating eccentric is not accomplishedthrough positive braking action, as many as nineteen revolutions andabout two seconds may be required before the eccentric speed passesthrough the resonance range.

In asphalt compaction, this extended period of resonance is unacceptableinsofar as grooves or ripples may be produced in the asphalt surface. Itwould, therefore, be highly desirable to provide for high force,positive, dynamic braking of the eccentric so as to substantiallyminimize the period of resonance, thereby rendering rollers vibrated byrotating eccentrics acceptable for asphalt compaction.

Moreover, it would also be desirable to provide for an acceleration rateof the eccentric, by means of a high power input, that would also avoidprolonged periods of resonance while bringing the eccentric to itsselected operating speed.

Patented Sept. 20, 1971 In many instances, the rotating eccentric meansis conveniently housed within the compacting roller for rotation aboutthe roller axis. Although such an assembly may be extremely desirable,it does present problems from both the standpoint of producingnon-uniformities in the surface being compacted and the standpoint oftractive eifort necessary for machine propulsion.

-For example, it has been found that as a result of rotation of theeccentric means, the freely rotatable compacting roller tends to beinduced to rotate in an angular direction opposite to that of theeccentric rotation. When the machine is stationary, the roller doesrotate in such a direction. The rate of this induced rotation of theroller is considerable when compared with the normally slow speed ofrotation of the roller induced by the slow vehicle propulsion during acompaction operation.

Thus, it is apparent that if the eccentric means is rotatable in onlyone direction, propulsion of the vehicle in at least one direction oftranslation tends to rotate the roller in a direction opposite to thedirection of rotation induced by the eccentric means. This produces atendency for the roller to slide along the surface and to causenonuniform compaction and cracks.

Moreover, the tractive effort needed to propel the vehicle in at leastone translating direction is unnecessarily increased by the inducedrotation of the roller in a reverse direction.

I'It would, therefore, be highly desirable to provide for two directionsof rotation of an eccentric means housed Within, and rotating about theaxis of, a freely rotatable compacting roller of a vibratory machine,and to correlate the direction of rotation of the eccentric means withthe direction of translation of the compacting machine.

Furthermore, it would be particularly advantageous to provide forautomatic reversing of the direction of rotation of the eccentric meansresponsive to changes in the direction of translation of the vehicle.Such automatic reversing would not only minimize the number of controlsthat need be regulated by an operator, but would also avoid thepossibility ofincorrect rotation correlation that may defeat thepurposes of a two-directional rotating eccentric means.

OBJECTS AND SUMMARY OF THE INVENTION It is, therefore, a general objectof the invention to provide a vibratory roller designed to obviateproblems of the type previously described.

It is a particular object of the invention to provide for rapid,positive, dynamic braking of a rotating eccentric means for a vibratorycompacting roller. l

It is a related object of the invention to provide a drive for arotating eccentric means of a vibratory compacting roller wherein a highpower input accomplishes rapid acceleration of the eccentric.

It is an independent object of the invention to provide driving meansfor a rotating eccentric means housed within, and rotatable about theaxis of, a vibrating compacting roller wherein the driving meansaccomplishes two-directional rotation of the eccentric means, with thedirection of rotation being correlated to the direction of translation'.y

It is a related object of the invention to provide a control for such adriving means that automatically correlates the direction of eccentricmeans rotation with the direction of vehicle translation.

It is yet another object of the invention to provide a method ofcompacting asphalt with a vibratory compacting roller by rotating aneccentric means mounted within the roller about the roller axis in anangular direction correlated with the direction of translation of thecompacting machine.

It is a still further object of the invention to provide an improvedmethod for compacting surfaces with a vibratory compacting roller byrapidly and dynamically decelerating a rotating eccentric means.

THE DRAWINGS Other objects and advantages of the present invention willbecome apparent from the following detailed description of a preferredembodiment as illustrated in the accompaying drawings, in which:

FIG. 1 is a schematic plan view of a self-propelled vibratory compactermachine according to a preferred ern- 'bodiment of the inventio-n;

FIG. 2 is a partial cross sectional view of the rotating eccentric meansused in the machine of FIG. l;

FIG. 3 is a perspective View illustrating the resilient mounting of thecompacting roller used in the machine of FIG. l;

FIG. 4 is a schematic illustration of the hydrostatic transmissionproviding the drive and brake for the ecentric means shown in FIG. 2;

FIG. 5 is a partial, perspective view of the pump illustrated in FIG. 4;

FIG. 6 is a schematic illustration of the control system for the machinepropulsion and eccentric means rotation;

FIG. 7A is a detailed plan view of the automatic eccentric meansrotation reversing linkage schematically illustrated in FIG. 6;

FIG. 7B is an end elevational view of the automatic reversing linkageshown in FIG. 7A; and

FIG. 8 is an elevational view of a memory throttle used in the controlsystem of FIG. 6.

DETAILED DESCRIPTION Referring now to FIG. 1, a schematic view of aselfpropelled vibratory compacting machine according to a preferredembodiment of the invention is there shown.

The machine includes a tractor frame 10 supported for ground traversingmovement on two spaced parallel wheels 12 and 14. These wheels, andtherefore the vehicle, are propelled in either a forward or reversedirection by a hydrostatic drive including a pump and a rnotor,respectively, schematically illustrated at 16 and 17. The pump of thisdrive is driven by an engine, schematically shown at 18, of any suitabletype.

Pivotally attached to the forward end of the tractor frame 10 formovement about a generally vertical axis 20 is a roller support frame22. This roller support frame 22 resiliently supports a freely rotatableroller 24.

Located within the roller 24, and mounted for independent rotation withrespect thereto, is a rotatable eccentric means. This eccentric means,as well as the resilient suspension of the roller 24, will behereinafter more fully described.

The direction of travel of the vehicle is controlled by a steering wheel28 mounted within the tractor frame 10 adjacent an opertaor seat 30.This steering Wheel is hydraulically coupled to a pair of spaced,parallel piston and cylinder assemblies 32 and 34. The pist-on rods ofthese assemblies are pivotally coupled to the roller support frame 22 onopposite sides of the generally vertical axis 20, as indicated at 36 and38.

It will be appreciated that reciprocation of the pistons of thesecylinder assemblies 32 and 34 provides for turning rnaneuverability lofthe vehicle by pivoting the roller support frame 22 of the integrated,self-propelled unit about the generally vertical attachment axis 20.

A drive motor 40 for rotating the eccentric means is mounted on theroller support frame 22 by supports (not shown). This motor ishydraulically coupled to a pump 42, mounted on the tractor frame 10, bymeans of a hose assembly 44. This pump 42 is driven by the engine 18.

The pump 42 and the motor 40i comprise a variable speed, reversiblehydrostatic transmission hereinafter more fully described in connectionwith FIGS. 4 and 5.

A propulsion throttle lever, schematically illustrated at 46 in FIG. 1,controls the direction and speed of rotation of the pump 16 ofhydrostatic propulsion transmission, and thereby controls the directionand speed of travel of the machine. This lever 46 is also operativelycoupled to an automatic direction control means 48 for the eccentric.This automatic control means 48 is hereinafter more fully described inconnection with FIGS. 6, 7A and 7B.

The control means `48 in turn is connected to the pump 42 of theeccentric means transmission, as indicated at 50.

The purpose of the control is to automatically correlate the directionof rotation of the eccentric means with the direction of translation ofthe vehicle. The speed of the eccentric is controlled by a memorythrottle 51.

Referring now to FIG. 2, the eccentric means for the roller 24 is thereshown. This eccentric means includes a shaft 52 extending coaxially intothe roller 24.

The shaft is mounted for rotation independently of the freely rotatableroller 24, for example, by means of bearings shown at 54. Within theconfines of the roller, the shaft 52 is provided with eccentric weightmeans 56 rotatable therewith. The shaft 52 is exibly connected by adrive connection 58 to a rotatble sheave 60.

This sheave 60 may be located within the contines of one of the sidegirders 62 of the frame 22 (FIG. 3). Suitable flexible drive belts 64connect the sheave to the output of the frame supported drive motor 40,as indicated at 66.

Output rotation of the motor 40 in either direction thereby causesrotation of the shaft 52 of the eccentric means in the same direction.As the shaft 52 is rotated, the eccentric Weight means 56 developsvibratory forces which cause vibratory oscillation of the resilientlymounted, independently rotatable roller 24.

In FIGS. 2 and 3, the resilient mounting of the compacting roller 24 onthe frame 22 is illustrated. The roller 24 is hollow, and generallycylindrical and is mounted for free rotation about a generallyhorizontal axis, indicated at 68.

The frame 22 includes front and rear ends 70 and 72, respectively, andlongitudinally extending side girders 62 and 74. These girders arehollow, box-like members in one of which the sheave 60 and exible drivemembers 64, as well as the nal output member 76 connected to the motor40, are located.

The roller 24 is provided with two axially recessed, radially extending,end plates 78 (only one of which is shown), each spaced laterallyinwardly from the adjacent one of the side girders 62 and 74. FiXedlysecured to the end plate 78, and concentric with the roller axis, aretwo hollow hubs indicated generally at 80. These hubs are supported forrotation in vertically supporting beams 82. The beams 82 are spacedlaterally from and are parallel to the adjacent side girders and arelocated within the c011- nes of a hollow, cylindrical, projection 84forming a continuation of the roller external surface.

Resilient suspension members 86 xedly connect each supporting beam 82 torigid spacing panels I88 mounted on the side girders. These resilientsuspension members 86 permit limited rela-tive motion between the roller24 and the frame 22 in all directions. For a more detailed descriptionof the resilient mounting for the roller, as well as the flexibleconnection 58 between the sheave 60 and eccentric shaft 52, referencemay be had to U.S. Pat. No. 3,411,420 (the disclosure of which is herebyincorporated by reference), assigned to the assignee of the presentinvention.

Referring now to FIG. 4, a schematic diagram of the previouslyidentified hydrostatic transmission for driving and positivelydecelerating the eccentric means is there shown. It will be appreciatedthat this transmission is conventional and forms no part of the presentinvention, per se. However, the transmission, when properly sized,provides for rapid acceleration, and positive dynamic braking of theeccentric means in about three revolutions thereof. This obviates theproblems associated with resonance between the roller support frame 22and the vibrating roller 24.

Moreover, this combination also permits control of the direction andspeed of rotation of the eccentric vibrating means, so as to minimizeproblems associated with both non-uniform compaction and unnecessarytractive effort required for propulsion of the machine. This isaccomplished by correlating the direction of rotation of the eccentricmeans with the direction of translation of the vehicle. Thus, the rolleris not induced, by the eccentric means rotation, to rotate in adirection opposite to that caused by machine translation.

The transmission is comprised of the previously identified reversible,variable displacement pump 42 and fixed displacement motor 40. The pump42 includes a housing 90 in which an input shaft 92 is mounted forrotation about the central axis thereof. Concentrically mounted aboutthe input shaft 92, and fixedly attached thereto, is a cylinder block 94(FIG. 5). Within this block a plurality of circumferentially spaced,longitudinally extending cylinders 96 are disposed in an annular ring.

Mounted for reciprocation within each of the cylinders 96 is a piston98. The rod ends of these pistons are generally spherical, as indicatedat 100, and are universally mounted in spherical shoes 102 which arerotatable with the cylinder block 94.

The variable displacement and reversing characteristics of the pump 42are provided by a swashplate 106. This swashplate 106 is mounted forpivotal motion solely about a single axis perpendicular to that of theinput shaft 92, and is stationary with respect to all otherperpendicular axes.

Control of the swashplate angle controls the displacement of the pumpand, therefore, the speed of the motor 20 and the eccentric means. Thisspeed control is provided by a control handle 108 operatively associatedwith a displacement control valve, schematically illustrated at 110.This control valve 110 is in lluid communication with rst and secondservo control cylinders 112 and 114, as indicated by flow lines 116 and118, respectively.

These servo cylinders 112 and 114 are located in the pump housing 90,and their pistons 120 and 122 are connected by respective pivot links124 and 125 to diametrically opposite portions of 4the swashplate, asindicated at 128- and 130.

A follow up linkage 132 is coupled to the swashplate as schematicallyillustrated at 134, to provide a feed back linkage system. Theswashplate 106 is spring-loaded to a neutral position, by springs 136(FIG. 5) to insure a positive neutral, i.e. no swashplate angle.

In FIG. 4, the control handle 108 is shown as pivoted clockwise toobtain a first direction on the swashplate angle corresponding to onedirection of rotation of the eccentric means. This is accomplished bypressurizing the one servo cylinder 112 while exhausting the other servocylinder 114 through the displacement control valve 110. If the oil inthe circuit becomes pressurized to a point that tends to overcome thepreset swashplate position, the follow up linkage 132, which connectsthe swashplate to the displacement control valve 110, activates thecontrol valve to supply adequate pressure to the extended servo piston,thereby to maintain the swashplate in its preset position.

It will be appreciated that since the control valve is spring centered,both servo cylinders 112 and 114 are equally pressurized when thecontrol handle 108 is in its neutral position (Le. vertical inconnection with the orientation shown in FIG. 4). Moreover, if thecontrol handle 108 is pivoted counterclockwise (as viewed in FIG. 4),the swashplate 106 will assume a tilt angle corresponding to thedirection of rotation of the eccentric means opposite to that caused bya clockwise movement of the handle.

With the swashplate at an angle, some of the piston rod ends 100 areextended and others depressed. Rotation of the cylinder block 94 thusresults in a flow from certain of the cylinders 96 and a suction by theremaining ones of these cylinders.

An annular valve plate 142 (FIG. 5) is mounted adjacent the end of thecylinder block. This valve plate is provided with a plurality ofopenings 144 to facilitate ow into and out of the cylinders of the pump.

The previously identified motor 40 is mounted on the roller supportframe 22, remote from the pump 42. However, this motor 40 is incontinuous, closed circuit, fluid communication with the pump 42 bymeans of flow lines 146 and 148. The parts of the motor aresubstantially identical to those of the pump 42 and will not bediscussed in detail. It will sutlice to say that the motor is of the xeddisplacement type, i.e. the motor swashplate 150 is at a constant anglewith respect to an axis perpendicular to the motor output shaft 151.

With the control handle in the clockwise pivoted position indicated inFIG. 4, high pressure oil exists in the lower flow line 148 between thepump and the motor 40'. Low pressure oil exists in the upper flow line146, between the motor 40 and the pump 42. The hydrostatic fluid causesthe motor output shaft 151 to rotate in the same angular direction asthe pump input shaft 92 as indicated by the arrows 153 and 152 (FIG. 4).

In order to provide oil in the transmission for cooling purposes, and toprovide oil under positive pressure on the low pressure side of thepump-motor circuit, a charge pump 154 is included in the system. Thischarge pump also provides suicient oil under pressure for controlpurposes and for internal leakage make-up. One of two identical chargepump check valves 156 and 158 directs the charged oil to the lowpressure side of the main circuit. The other check valve is maintainedin closed position by the high pressure oil on the other side of themain circuit.

As will be apparent, hydrostatic oil exists in the main circuit in acontinuous closed loop. The quantity of oil displaced is a function ofthe pump speed and the amount of tilt of the swashplate. This controlsthe speed of the eccentric means. The direction of oil displacement isdetermined by the orientation of the tilt angle of the pump swashplate.This controls the direction of rotation of the eccentric means.

A manifold valve assembly 160, including two high pressure relief valves162 and 164, a shuttle valve 166 and a charge pressure relief valve 168,is connected across the main fluid circuit. The pressure relief valves162 and 164 prevent any sustained abnormal pressure surges in either ofthe main circuit ow lines 146 and 148. During rapid acceleration ordeceleration, as well as in response to a sudden load application, theserelief valves 162 and 164 dump oil from the high pressure line to thelow pressure line of the main circuit.

The shuttle valve 166- establishes a fluid circuit between the lowpressure main circuit line (146 in FIG. 4) and the charge pressurerelief valve 168. In the event that excess cooling oil is added to thecircuit by the charge pump 154, this excess cooling oil is therebyremoved by the charge pressure relief Valve 168. It will also 'beapparent that the charge pressure relief valve 168 functions to controlthe charge pressure level.

Since the shuttle valve 166 is centered by springs (not shown) to aclosed position, none of the high pressure oil is lost from the circuitduring the transition of high pressure and low pressure between the maincircuit lines 14 and 148. t

Excess oil that may exit from the charge pressure relief valve 168enters the motor casing and flows to the pump casing through a free flowoil line 170. Thus, the charge pump cooling oil is circulated to aid incooling. Cooling oil exiting from the pump casing, as indicated at 172,passes through a heat exchanger 174 and is returned to a reservoir 176.A lvalved bypass circuit 178 is provided at the heat exchanger 174 toprevent back pressure that may be caused by cold oil.

At times when the main pump 42 is in neutral, the shuttle valve 166 isnormally closed. A charge relief valve 180 in the charge pump 154directs excess oil from the charge pump to the cooling circuit in suchinstances. It will be appreciated that under such conditions, coolingflow is not admitted to the motor. However, the motor being at rest, andthe eccentric means being stationary, such cooling llow is notnecessary.

As previously mentioned, the output shaft 151 of the motor 40 isoperatively coupled to the sheave 60 by the flexible belts 64. Wit-h thepump 42 and motor 40 of the transmission in continuous closed-loopcommunication, and with the charge pressure in the closed-loopconstantly maintained, substantially instantaneous, hydrostatic responseis obtained in the rotation of the eccentric means by movement of thetransmission control handle 108.

No clutch is necessary between the motor and the eccentric means.Moreover, the closed-loop system insures positive, and immediate dynamicbraking of the vibrating means. It is apparent that means for positivelybraking the eccentric means, other than the hydrostatic transmissiondescribed, .are within the scope of the invention.

The control handle 108 is stepless, and therefore the direction andspeed of rotation of the eccentric means is potentially infinitelyvariable from zero to its maximum value.

For a more detailed description of the structure and mode of operationof the transmission, reference may be had to the Engineering ApplicationManual, Bulletin 9566, available from Sundstrand Hydro-Transmission,LaSalle, Ill. The disclosure of the bulletin is hereby incorporated byreference.

Referring now to FIG. 6, a schematic diagram of the control system forthe propulsion transmission and the vibrating means transmission isthere shown.

The previously identified propulsion control throttle 46 is pivotallymounted at a convenient location in the tractor frame for manipulationby an operator. A Bowden cable 184 attached to one end of this throttle46, as indicated at 186, is coupled to the propulsion transmission pumpschematically illustrated at 16.

Movement of this cable 184 controls the angle of a swashplate in thepump of the' propulsion transmission. This transmission may besubstantially identical to that described in connection with theeccentric means control.

Thus, the direction of propulsion, as well as the speed, may becontrolled by operation of the stepless propulsion control throttle 46between the dotted positions shown.

In FIG. 6, the previously identied memory type control throttle 51,hereinafter more fully described, is schematically shown. This throttle51 controls the speed of the eccentric means. In order to obviate thenecessity of the operator having to correlate the direction of rotationof the eccentric means with that of the machine translation, thepreviously described automatic direction control means schematicallyshown at 48 is provided. This control means 48 functions to correlatethe direction of rotation of the eccentric means with the direction -ofmachine translation.

A second Bowden cable 194 is connected to the end of the propulsionthrottle 46 adjacent the first Bowden cable 184. This second cable 194is operative to move a switching link 196 to either of two positions,corresponding respectively to forward land reverse translation movementof the machine. In one of these positions, the switching link 196 isoperative by means of a third liexible Bowden cable 198 to pivot theswashplate control handle 108 counterclockvw'se.

In the other position of the switching link 196, the cable 198 causesthe swashplate control handle 108 to pivot clockwise. Thus, the operatorneed only move the eccentric means control throttle S1 between its stopand pivoted positions in one angular direction. The position of thepropulsion control throttle 46 will automatically insure a correctdirection of rotation of the eccentric means by displacement of theswitching link 196.

Referring now to FIGS. 7A and 7B, the vibrating means direction controlmeans 48 is there shown in detail. This control means includes a supportbracket 200 on which the end of the sleeve of the second Bowden cable194, remote from the propulsion control throttle 46, is monuted, asindicated at 202. The end of the Bowden cable 194 itself is attached tothe control link 196 as indicated at 204.

`One end of the control link 196 is pivotally attached to one end of adrag lever 206 as indicated lat 208.` This drag lever 206 is in turnpivotally mounted on the support bracket 200, as indicated at 210, formovement to any pi'votal position between two stops 212 and 214 onopposite sides of the pivot axis. The other end of the drag lever 206 isconnected to a fourth Bowden cable 216- (FIG. 6), the remote end ofwhich is coupled to the memory throttle 51.

The free end of the control link 196 is provided with an enlargedcamming head 218 having a transversely extending, curved camming groove220 in a projecting end thereof. This camming groove 220 faces towardthe bracket 200 and is generally superposed above a follower lever 222.

The follower lever 222 is pivotally mounted on the bracket 200 asindicated at 224. Provided on the follower lever and equally spaced onopposite sides of the pivot point, are two generally cylindricalfollower projections 226 and 228 which face the camming groove 220. Oneend of the follower lever 222 is connected to the previously identifiedthird Bowdencable 198, the other end of this cable 198 being attached tothe control handle 108 of the rvariable displacement pump 42 (FIG. 6).

When the memory throttle 51 is in its full line, or stop position (asshown in FIG. 6), the drag lever 206 is in its off position, adjacentone stop 214. When the propulsion throttle 46 is in is full line or stopposition (as shown in FIG. 6), the curved camming groove 220 of thecontrol links 196 remains between the cylindrical followers 226 and 228.

'Pivotal movement of the propulsion throttle 46 in one direction causesthe second Bowden cable 194 to move the control link clockwise about thepivot axis 208 at the point of connection between the control link andthe drag lever 206. Thus, one cylindrical follower 226 is receivedwithin the curved camming groove 220.

At this point, pivotal movement of the memory throttle 51 moves the draglink 206 clockwise about its pivot point 210, to thereby drag thecontrol link 196` and cause pivotal movement of the follower lever 222in a clockwise direction. This movement in turn pivots the swashplatecontrol handle 108, by means of the third Bowden cable 1918, to causerotation of the eccentric means in one direction, as previouslydescribed.

When the direction of propulsion is to be reversed, the memory throttle51 is brought back to its full line, or stop position. Through the draglever 206, the control link 196 causes the follower lever 222 to bringthe control handle 108 of the pump 42 to its neutral position, therebydynamically and positively braking the eccentric means.

The propulsion throttle 4'6 is now pivoted in an opposite directionwhich causes the control link 196 to pivot counterclockwise about theaxis 208 as viewed in FIG. 7. The second cylindrical follower 228 is nowreceived within the camming groove 220. Pivotal motion of the memorythrottle 51, which causes dragging of the control link 196 through thedrag lever 206, now moves the follower lever 222 in a counterclockwisedirection. Therefore, the control handle 108 of the pump 42 is pivotedin an opposite direction so as to reverse the direction of rotation ofthe eccentric means and correlate that direction with the direction oftranslation of the vehicle.

It will be appreciated that if the direction of propulsion of thevehicle is reversed without bringing the eccentric means to a stop, thecontrol link 196 will still be pivoted about its displaced axis 208, andthe cur-ved camming groove 202 will ride over the follower projection,

thereby leaving the follower lever in its pivoted position. Thus, toreverse the direction of rotation of the eccentric means, it will benecessary to bring the memory throttle back to its stop position. Thiswill cause one of the at end faces 230 and 231 of the camming head 218to move the follower lever to its neutral position, and then the correctcylindrical follower projection will move into the slot as the controllink continues to pivot `about its axis 208 under the action of theBowden cable 194.

In order to avoid the necessity for'an operator having to continuouslyselect the proper pivotal position of the eccentric control throttlewhen bringing the eccentric means into operation, the eccentric controlthrottle is constructed as a memory throttle, as best seen in FIG. 8.This memory throttle 51 is provided with a longitudinally extending slot232 in which one end of an adjustable link 233 (shown in phantom in FIG.8) is constrained for slidable movement.

The other end of the adjustable link 233 is constrained for slidablemovement in a longitudinally extending slot 234 in a bracket 236. Whenthe memory throttle 5-1 is in its fully pivoted position (FIG. 8), thelink constraining slots 232 and 234 are generally aligned. Pivotalmovement of the throttle beyond this point is prevented by a suitableover center lock (not shown).

Pivotal movement of the memory throttle 51 about an axis 238 on thebracket 236 moves the link 233 within the slots 232 and 234. The fourthBowden cable 216 is attached to the bracket end of the adjustable link233 so as to control movement of the drag lever 206 of the control means48.

In order that the memory throttle 51 need only be moved between its stopand a fully pivoted position once a preferred rotational speed of theeccentric means has been determined, the position of the adjustable link233 within the throttle slot 232 is controlled by a micrometer head 240.With the micrometer head properly adjusted, a full throw of the memorythrottle 51 will provide a proper movement of the pump control handle108 through the linkage of the automatic control means 48. This movementof the control handle 108 moves the swashplate of the pump to thedesired angle corresponding to the selected speed of eccentric means.

It will be appreciated that the control means 48 automaticallycorrelates the direction of tilt of the swashplate (and therefore thedirection of rotation of the eccentric means) with the direction ofpropulsion of the vehicle.

Operation of the self-propelled vibration compacting machine of thepresent invention may now be described. The operator selects thedirection and speed of machine movement by proper positioning of thepropulsion control throttle 46. The machine may be maneuvered from thestraight line path by control of the steering wheel 2|8 which causes thepiston and cylinder assemblies 32 and 34 on the tractor frame 10 topivot the roller support frame 22 by a selected amount about thegenerally vertical axis 20.

With the machine moving in the forward direction and with the eccentricmeans control throttle 51 moved to a pivoted position, the eccentricmeans rotates in an angular direction tending to induce rotation of theroller in the same direction of roller rotation induced by propulsion ofthe machine. In this way, uniformity in compaction of the asphalt orother surface is promoted and tractive eiort necessary to propel thevehicle is reduced rather than increased by rotation of the eccentricmeans.

Before reversing the direction of the vibratory compacting machine, therotating eccentric means is stopped by moving the eccentric meanscontrol throttle 51 to its stop position (full line as shown in FIG. 6).The tight, closed-loop fluid circuit between the pump 42 and the motor40 of the vibrator transmission causes immediate, positive dynamicbraking of the eccentric means. With a properly sized transmission ofthe type previously described, and a resonance speed peak of about l600r.p.m., the rotating eccentric means was positively decelerated througha resonance range of about 240 r.p.m. from an initial speed of about15000 r.p.m., in about three revolutions thereof. The positively brakedeccentric means is thus moved through the resonance range in aboutonethird of a second. This may be particularly attributed to the factthat the motor 40 has a substantially constant torque over a wide speedrange.

When the direction of machine propulsion is reversed, and the eccentricmeans control throttle 51 is pivoted to operating position, theautomatic direction control means 48 automatically reverses thedirection of rotation of the eccentrics 56.

When the memory throttle 51 is employed, once the memory system is set,as previously described, it is only necessary for the operator to movethe throttle `51 between full speed and stop positions, immediatelybefore and during translation direction changes. The speed of theeccentric means will be controlled by the memory.

It will be appreciated that the eccentric speed passes through theresonant range during acceleration in substantially the same time as itdoes during deceleration.

SUMMARY OF ADVANTAGES Thus it will be seen that in following the presentinvention, an improved vibrating machine is provided.

-Particularly significant is the provision for positive braking of arotatable eccentric means.

Also of importance is the reversible driving of an eccentric meansmounted for rotation about the axis of the tamping roller. With such anarrangement, tractive effort necessary for machine propulsion isminimized, and skipping or bumping of the roller as a result ofrotational forces on lthe roller generated by the rotating eccentricmeans is eliminated.

Of related importanceis the automatic control that correlates thedirection of rotation of the eccentric with the direction of translationof the machine without operator intervention.

Moreover, the hydrostatic transmission, with a closedloop, tight circuitbetween the variable displacement pump and the xed displacement motor,eliminates the need for clutches between the transmission and theeccentric and the need for valving in the system such as that requiredin hydrodynamic circuits. This feature in combination with the rotatableeccentric means provides the rapid response necessary for minimizingproblems associated with resonance.

Although the invention has been described with reference to onepreferred illustrated embodiment, it will be appreciated by thoseskilled in the art that additions, modiiications, substitutions,deletions and other changes not specifically described may be made whichfall Within the spirit of the invention.

What is claimed is:

1. In a vibratory compacter of the type including a frame, a freelyrotatable compacting roller resiliently mounted on the frame, andeccentric means rotatable about the roller axis for vibrating thecompacting roller, the improvement comprising:

reversible and variable speed hydrostatic transmission means,continuously coupled to said eccentric means and comprised of a pump andmotor in closed loop fluid circuit, for selectively rotatably drivingsaid eccentric means in each of two directions of rotation at a speedgreater than the range of speeds at which resonance exists between saidframe and said compacting roller, and for rapidly, positively anddynamically braking said eccentric means through the range of speeds atwhich resonance exists between said frame and said compacting roller.

2. The improvement according to claim 1 wherein said hydrostatictransmission means comprises:

a reversible variable displacement pump,

a xed displacement motor, said fixed displacement motor being iiuidcoupled to said variable displacement pump by a closed loop, tight fluidcircuit.

3. In a translatable vibratory compacter of the type including aresiliently mounted and freely rotatable compacting roller, andeccentric means rotatable about the roller axis for vibrating thecompacting roller, the improvement comprising:

means for selectively rotatably driving said eccentric means in each oftwo directions of rotation, and for positively braking said eccentricmeans, and control means responsive to the direction of translation ofsaid vibratory compacter and connected to said means for selectivelydriving and positively braking said eccentric means, for correlating thedirection of rotation of said eccentric means with the direction oftranslation of said vibratory compacter.

4. A vibratory compacter comprising:

a translatable support frame;

v a compacting roller resiliently mounted on said support frame forcompacting engagement with the ground,

rotatable eccentric means for vibrating said compacting roller, and

variable speed hydrostatic transmission means, comprised of a pump andmotor in closed loop liuid circuit, for rotating said eccentric means ata speed greater than the range of speeds at which resonance existsbetween said frame and said compacting roller and for rapidly,positively and dynamically braking said rotatable eccentric meansthrough the range of speeds at which resonance exists between said frameand said compacting roller.

5. The vibratory compacter according to claim 4 wherein said hydrostatictransmission means comprises:

a variable displacement pump,

a fixed displacement motor, said xed displacement motor being tluidcoupled to said variable displacement pump by a closed loop, tight fluidcircuit, and being continuously connected to said rotatable eccentricmeans.

6. A vibratory compacter according to claim 4 wherein:

said rotatable eccentric means is selectively rotatable in each of twoangular directions about the axis of said roller, and Y said hydrostatictransmission means comprises means for selectively rotating saidrotatable eccentric means in each of said two angular directionscorrelatable with the direction of translation of the frame.

7. A translatable vibratory compacter comprising:

a support frame,

a compacting roller resiliently mounted on said support frame forcompacting engagement with the ground,

rotatable, eccentric means for vibrating said compacting roller, andselectively rotatable in each of two angular directions about the axisof said roller,

hydrostatic means for selectively rotating said rotatable eccentricmeans in each of said two angular directions at a speed greater than therange of speeds at lwhich resonance exists between said frame and saidcompacting roller, and for positiv-ely braking said rotatable eccentricmeans through the range of speeds at which resonance exists between saidframe and said compacting roller and said hydrostatic means comprising ahydrostatic transmission including a variable displacement pump,

a iixed displacement motor, said ixed displacement motor being fluidcoupled to said variable displacement pump by a closed loop, tight fluidcircuit, and being continuously connected to said rotating eccentricmeans, and

control means responsive to the direction of translation of saidvibratory compacter, and connected to said means for rotating saideccentric means, for correlating the direction of rotation of saideccentric means with the direction of translation of said vibratorycompacter.

8. A vibratory compacter comprising:

a frame,

means supporting said frame for selective ground traversing movement inforward and reverse directions,

a compacting roller mounted on said support frame for compactingengagement with the ground,

rotatable, leccentric means, mounted for rotation about the axis of saidcompacting roller, for vibrating said compacting roller, said rotatableeccentric means being selectively rotatable in each of two angulardirections,

means for selectively propelling said frame in the forward and reversedirections, and

means, responsive to the direction of translation of said frame, forselectively rotating said eccentric means in each of said two angulardirections in correlation With the direction of translation of saidframe.

9. A vibratory compacter according to claim 8 wherein said means forselectively rotating said eccentric means includes:

control linkage means, operatively connected to said means forselectively propelling said frame in forward and reverse directions, forautomatically correlating the direction of rotation of said eccentricmeans with the direction of translation of said frame.

10. A vibratory compacter according to claim 8 wherein:

said means for selectively rotating said eccentric means comprises ahydrostatic transmission including a reversible, variable displacementpump,

a fixed displacement motor, said fixed displacement motor being fluidcoupled to said variable displacement pump by a closed loop, tight fluidcircuit, and being continuously coupled to said eccentric means, and

means for reversing said pump to reverse the direction of rotation ofsaid eccentric means.

11. A vibratory compacter according to claim 8 including:

12. A vibratory compacter according to claim 11 wherein:

said means for selectively rotating said eccentric means, and said meansfor positively braking said eccentric means together comprise a singlehydrostatic transmission including a reversible, variable displacementpump,

a iixed displacement motor, said -ixed displacement motor being iiuidcoupled to said variable displacement pump by a closed-loop, tight Huidcircuit, and being continuously coupled to said rotatable eccentricmeans.

13. A vibratory compacter comprising:

a frame,

means supporting said frame for selective ground traversing movement inforward and reverse directions,

a compacting roller mounted on said frame for compacting engagement withthe ground,

rotatable eccentric means, mounted for rotation about the axis of saidcompacting roller, for vibrating said compacting roller at a rateindependent of frame propulsion rate, said rotatable eccentric meansbeing selectively rotatable in each of two angular directions,

means for selectively propelling said frame in the forward and reversedirections and rotating said roller in opposite directions during framepropulsion in forward and reverse directions, and

means for selectively rotating said eccentric means in each of said twoangular directions correlatable with the direction of translation ofsaid frame,

said means for selectively rotating said eccentric means in each of saidtwo angular directions correlatable with the direction of translation ofsaid frame including an adjustable lever having a neutral position atwhich no rotation is .imparted to said eccentric means and activepositions on opposite sides of said neutral position,

said lever being movable to an active position on one side of saidneutral position for rotating said eccentric means in a rst directiontending to induce compacting roller rotation in the same direction asthat produced during a forward movement of said frame, and said leverbeing movable to an active position on the opposite side of said neutralposition for rotating said eccentric means in a second direction tendingto induce compacting roller rotation in the same direction as thatproduced during a reverse `movement of said frame.

14. A vibratory compacter comprising:

a frame,

means supporting said frame for selective ground traversing movement inforward and reverse directions,

a compacting roller mounted on said frame for compacting engagement withthe ground,

rotatable, eccentric means, mounted for rotation about the axis of saidcompacting roller, for vibrating said compacting roller, said rotatableeccentric means being selectively rotatable in each of two angulardirections,

means for selectively propelling said frame in the forward and reversedirections, and

means for selectively rotating said eccentric means in each of said twoangular directions correlatable with the direction of translation ofsaid frame,

said means for selectively rotating said eccentric means in each of saidtwo angular directions correlatable with the direction of translation ofsaid frame including adjustable memory throttle means for maintainingthe speed of rotation of said eccentric means substantially identical ineach of said two angular directions. '15. A method of compacting a roadsurface with a vibratory compacter of the type including a propellableframe on -which a freely rotatable compacting roller is mounted forvibratory engagement with the ground, and further including an eccentricmeans, mounted for twodirectional rotation about the axis of the roller,for vibrating the roller at a rate independent of frame propulsion rate,the method comprising the steps of:

propelling the frame and the roller in a first translating directionover the road surface and thereby causing the roller to rotate in aclockwise direction, and simultaneously rotating the eccentric means ina rst angular direction tending to induce rotation of the roller in aclockwise direction; and

subsequently propelling the frame and the roller in an oppositetranslating direction and thereby causing the roller to rotate in acounterclockwise direction, and si-multaneously rotating the eccentricmeans in a second angular direction tending to induce roller rotation ina counterclockwise direction.

16. The method according to claim 15 wherein the roller is resilientlymounted on the frame, the method including the step of dynamicallybraking the eccentric means prior to changing the direction of rotationof the eccentric means and the direction of translation of the frame androller.

References Cited UNITED STATES PATENTS 2,938,438 5/ 1960 Hamilton 94-483,395,626 8/1968 Garis 94-50 3,411,420 11/1968 Martin 94-50 3,416,41912/1968 Kronholm 94-50 3,450,012 6/ 1969 Beierlein 94-50X 3,453,939 7/1969 Pollitz 94-46 40 JACOB L. NACKENOFF, Primary Examiner

